1. Field of the Invention
The invention relates to a system for characterizing skin condition.
2. Description of Related Art
Human skin secretes oil, most noticeably on the face and scalp, to prevent water loss from the skin surface and protect the skin against infection by bacteria and fungi. Skin oil is a complex mixture of sebum, lipids from the surface skin cells, sweat, and environmental material. Sebum, a variable mixture of lipids produced by sebaceous glands in the skin, contains mostly glycerides and free fatty acids in addition to wax esters, squalene, cholesterol esters, and cholesterol. While most of the sebaceous glands open out into the hair follicle, some open directly onto the skin surface. Because sebum constitutes a significant portion of skin oil, some people generically use the term “sebum” to describe all skin oil; however, technically sebum is only one of the oily substances on the surface of the skin.
The rate at which oil is produced and secreted to the surface of the skin varies greatly from person to person. Because androgens, commonly referred to as sex hormones, regulate sebum production, the quantity and distribution of sebum varies with sex and age and can be altered by disease and medications. Additionally, seasonal and environmental changes can significantly impact the amount of sebum present on the skin's surface.
Facial cosmetics and beauty products are formulated for use with distinct skin types, but it is often challenging to visually determine the skin condition of the face. As a result, the selection of appropriate facial cosmetics is often arbitrary, sometimes difficult, and often costly. Furthermore, the amount of sebum secreted to the skin's surface is not constant across the many areas of the face due to the increased size and number of sebaceous glands on the forehead and chin. This makes the selection and application of suitable facial products even more problematical.
Systems have been developed to quantify oil production and characterize skin type. For example, U.S. Pat. No. 4,313,393 to Barbuscio et al. describes an indicating device with a sheet material treated with an oil-soluble dye surrounded by a transparent permeable membrane. The strip is applied to a certain area on the hair or scalp, and skin oil present in the area permeates the membrane and is absorbed by the dye-treated material. As the oil contacts and solubilizes the dye, a visual color change occurs. A standardized comparison chart is used to assess the degree of oil in the tested area of the hair/scalp. In U.S. Pat. No. 4,981,145 to Goldstein, a sampling device with absorbent sheets is attached to the facial skin surface with a headband for a predetermined period of time, approximately 3 hours. After removal, the device is folded, sealed, and mailed to a test laboratory where skin oil content is determined by weighing methods.
Other systems are based on the fact that skin oil deposited on a translucent element causes that element to become transparent. For example, U.S. Pat. No. 5,094,248 to Kawam describes a translucent microporous polymeric film that absorbs and retains oil when applied to the skin manually or with a professional device for 5-30 seconds. The used film is positioned in front of a dark background to create a pattern through the transparent areas, and the pattern is compared to several references for skin type characterization.
The devices and systems developed thus far have been deficient in several aspects. The tape or sheet systems have a small surface area relative to the size of the face and, therefore, they only measure the oiliness for the specific area to which the tape is applied. In addition, these laminar-type systems are difficult to apply evenly and with consistent skin contact over the contours of an item with complex topography such as the human face. As discussed above, insufficient information regarding the entire face could lead to application of inappropriate facial products. Additionally, the devices cannot be confidently self-administered; either a professional is required to apply the system or special meters or equipment are needed to determine the results.